Its as much of a hint to RS remakes as it is to RBY remakes... I mean if it was Magma/Aqua grunts in BW and then changed to Rocket grunt in BW2, someone would say that its a hint for RS remakes because they were taken out.

Also that's barely a spoiler, since the world tournament is in the trailers already..
Not sure where you were going with timelines, but as far as the tournament goes, you can be 100% sure the people appearing in it are not canon. Its just a postgame extra feature, not part of the story, otherwise as you say they would all look different/older, since with Caitlin does.

And again, there is simply no way for whatever next game to be "included in this generation". As there is an unavoidable handheld change to happen with whatever follows.

Back to the hints-topic:
There have been as many RS hints as for any other game or generation. There is always references between the games and reoccurring people and all sorts of things. There have never been "omg undeniable hint for upcoming game" in any games. Unless you count self-explanatory inclusions of third mascots in initial duo of games as hint?.....

My friend it's not like Nintendo would start development on R/S remakes two days before they announce it. So development could of started early 2012 or late 2011 when the DS was less dead. Besides I believe Nintendo plan things before they do it. R/S remakes for the DS could be part of the plan. It may not make sense to you but then again your not the creator of the second most popular media franchise in the world( video game wise)
But again I could be wrong. I have no facts to back up my arguments